code: def main() -> None:
      parser = argparse.ArgumentParser(
          description="test files should have main block linter",
          fromfile_prefix_chars="@",
      )
      parser.add_argument(
          "filenames",
          nargs="+",
          help="paths to lint",
      )
  
      args = parser.parse_args()
  
      pool = mp.Pool(8)
      lint_messages = pool.map(check_file, args.filenames)
      pool.close()
      pool.join()
  
      flat_lint_messages = []
      for sublist in lint_messages:
          flat_lint_messages.extend(sublist)
  
      for lint_message in flat_lint_messages:
          print(json.dumps(lint_message._asdict()), flush=True)
  
file_path: pytorch/tools/linter/adapters/test_has_main_linter.py
imports: import argparse
  import json
  import multiprocessing
  from enum import Enum
  from typing import List, NamedTuple, Optional
  import libcst
  import libcst.matchers
label_desc: Use image node_id 2 for calling a global function with example usage: main() without return types